Program-controlled switching equipment serve the purpose of connecting communication terminal equipment to one another and of connecting these terminal equipment to communication networks, particularly public networks. The variety of known switching equipment extends from simple telephone exchange systems for the exclusive transmission of voice up to complex ISDN communication systems having simultaneous multiple communication or even mixed communication of voice, text, image and data. A communication system of this latter type is known from a special issue of "TELCOM Report" -- ISDN im Buero, 1985, ISBN 3-8009-3846-4, Siemens AG.
Regardless of their degree of complexity, switching equipment are to be fundamentally understood as being digital data processing systems that have a close functional relationship to a plurality of periphery units related to the switching technique. The program-oriented part, generally referred to as system software, of a switching equipment is usually structured task-oriented or, respectively, function-oriented and is divided into a call processing software component, a dependability software component and an administration and maintenance software component. A respective plurality of function-related program modules whose processing in the form of what are referred to as "tasks" is coordinated by a multitasking operating system belongs to each of these software components.
Within the call processing software, which can be subdivided into the function complexes of peripheral processing, blind technology and switching technology, the peripheral processing essentially carries out data and information transport functions. The line technology has the job of matching the interface of the peripheral processing of the ISDN interface to the switching technology. The switching technology produces the actual performances for the user surface of the terminal equipment or, respectively, for the interfaces to the various networks.
The dependability software collects occurring error signals from software and hardware complexes and initiates the steps required in order to eliminate errors, to replace malfunctioning function complexes by others, and to display corresponding error messages on a service terminal that can be connected to the switching equipment.
What is meant by administration and maintenance is the administration and maintenance software of the switching equipment that is provided for the purpose of enabling the commissioning and maintaining as well as the control of the entire switching equipment. This also includes the activation and deactivation of system functions as well as the acquisition and archiving of all operational modifications of the overall system.
In a certain sense, the administration and maintenance represents an interface to the function setting of a program-controlled switching equipment. This interface is based on a plurality of individual administration and maintenance instructions that are structured according to switching-oriented points of view and, so to speak, represent the basic structure for influencing the switching equipment. The administration and maintenance related information deposited in a database of the switching equipment, which define the behavior and the functioning of the switching equipment, for example with respect to the connected subscriber terminal equipment, can be directly influenced with a majority of the individual administration and maintenance instructions available.
In the initially cited reference, these individual administration and maintenance instructions are referred to as "AMO" on page 104ff (Administration Maintenance Order). Further information about the structuring and implementation of administration and maintenance oriented components in a program-controlled switching equipment may be derived from European reference EP-0 477 414.
In many instances, particularly given medium and smaller systems, the possibilities for influencing the behavior and the functioning of a switching equipment created by this administration and maintenance interface have provided a degree of variability that, seen from the cost/benefit aspect, allows a loadability of the system software to seem not absolutely necessary. In many switching equipment, the software was therefore deposited in read-only memories that are usually fashioned as a "ROM" and that are contacted on assemblies of the switching equipment.
The advantages of depositing the system software in read-only memories, these lying, for example, in a faster "run-up" of the system or in a lower apparatus-oriented and, thus, financial outlay, are always opposed by a greater outlay in order to undertake modifications of the system software, for example, in order to implement new performance features, protocol operations or new functionalities. All read-only memories, namely, must usually be replaced for this purpose.